Ooh, I know the answer to this one !!!
The best (and pretty much only) bouldering around Montpellier is near the town of Lodeve.
Le Prieuré and Salces have really nice sandstone blocs. Both spots are in the woods and have a good grade range.
Loads of pictures/vids/etc here :
http://lodevebloc.blogspot.com/. It's worth buying the topo for Le Prieuré - only 3€.
There are small limestone bouldering venues in St Jean de Vedas and Castelnau le lez, but they're only worth an afternoon if you're desperate.
Montpellier itself is a really nice town. Not too big, lots going on.
There are two climbing walls, both run by Altissimo:
http://www.altissimo-escalade.com/. The Odysseum wall is right near a Tram stop, so easy to get to. The Grabels wall is a bit more hardcore. Both have smallish bouldering areas and BIG lead walls (ropes are supplied...).
There are two climbing shops,
expé near the town center and
Le Yeti in a village called Jacou.
You don't say when you might be around, but it's possible to climb all year round - Le Prieuré gets a bit green in winter and very hot in summer, but there's always something to do. Local sport crags are St Bauzille de Montmel, Claret and Thaurac (closest to furthest). Sunny in the winter, shady on summer evenings.
PS it's a VERY long drive to Annot, Targasonne and Font from Montpellier